A ghoul queen is an infrequently seen monster in SLASH'EM, not being randomly generated. They appear in the Temple of Moloch, and can also be generated by the summon undead spell ("Undead creatures are called forth from the grave!") that liches gain in SLASH'EM.

Oftentimes, one will find ghoul queens able to summon nasties. Like the vampire mage, they are not covetous, and so will not warp away after being hit a few times. Their dual spellcasting attacks make them quite dangerous, as they are quite able to quickly fill the level with nasties. Even in melee combat they are dangerous, as they are quite likely to curse your items. An artifact weapon that does double damage against them is advisable; in general, the large number of undead spellcasters in SLASH'EM makes Sunsword quite an appealing weapon, for those who can obtain it.

The forces of the gloom know each other, and are strangely
balanced by each other. Teeth and claws fear what they cannot
grasp. Blood-drinking bestiality, voracious appetites, hunger
in search of prey, the armed instincts of nails and jaws which
have for source and aim the belly, glare and smell out
uneasily the impassive spectral forms straying beneath a
shroud, erect in its vague and shuddering robe, and which seem
to them to live with a dead and terrible life. These
brutalities, which are only matter, entertain a confused fear
of having to deal with the immense obscurity condensed into an
unknown being. A black figure barring the way stops the wild
beast short. That which emerges from the cemetery intimidates
and disconcerts that which emerges from the cave; the
ferocious fear the sinister; wolves recoil when they encounter
a ghoul.